Además de no servir para absolutamente nada, costó un potosí.Apart from being of absolutely no use whatsoever, it cost a fortune.

The exotic-sounding word potosí in this idiom is from Potosí, a city in Bolivia which is one of the highest in the world, at an altitude of 4066 metres (13,340 feet). Silver was discovered there in 1545 by the Spanish colonizers of Latin America, and exported back to Spain in such vast quantities that the name of the city became a byword for something fabulously expensive.